By Holly Revelle, RSM Thailand July 2025 Intern from Bristol, United Kingdom

This article focuses on the legal requirements and practical considerations of making a Will in both districts and it has become a more topical subject in recent times with the chosen beneficiaries of the deceased often facing numerous inheritance problems. The RSM Law firm in Thailand has over the years provided multiple consulting advice to expatriates or beneficiaries of deceased persons pertaining to Wills and how they can be correctly prepared so that they are legally enforceable. We hope you find this information useful, and we look forward to your feedback.

What is estate planning?

It is the process of organising what will happen to your assets after your death or during incapacitation. Having a valid Will is one of the most responsible things you can do for family members and loved ones, as without it there could be considerable negative financial and emotional consequences.

Why cross-border planning matters?

For expats, dual nationals, or anyone with assets in both the UK and Thailand, cross-border estate planning requires dual Wills and careful drafting to ensure wishes are enforceable in both districts, and legal complications are minimised. The legalities of how assets of individuals are distributable to beneficiaries after death are dependent on the laws of each country. This means that immovable assets like property, are subject to the law where they are situated. Movable assets follow the law of domicile. This refers to your personal home or legal residence, where you are subject to personal legal obligations (an individual can only have one domicile at a time). The law determines which court has authority over personal matters and which laws apply to issues like inheritance, taxation, marriage, divorce, etc. Additionally, you want to avoid probate overlap, meaning that only having one Will may not always be sufficient. This means dual Wills help avoid conflicting instructions and accidental revocation.

Legal Framework:

In the UK, a valid Will typically requires you to be eighteen or older and of sound mind. It must be in written format, signed in the presence of two witnesses (they all must sign), and in the English language – this is under the Wills Act 1837. The UK law recognises Wills which are valid abroad.

Thai Wills are governed and controlled by the Civil and Commercial Code (CCC). A Will is valid if made in one of the legally recognized forms. The most usual form is a written Will under Section 1656 of the CCC which requires the testator to be at least fifteen years of age, of sound mind, and to execute the Will in the presence of at least two witnesses. Not all Wills require the involvement of a government officer. Only the public document Will (Section 1658) must be executed before a district officer together with witnesses, which provides a higher degree of certainty and minimizes later challenges to validity. In certain circumstances a holographic or oral Will is legally enforceable. The language of the Will must be in Thai, or for foreign Wills, accompanied by a Thai translation.

It is best to appoint a Thai executor to oversee the probate. Foreign Will recognition is possible but is more complicated than the UK. It requires translation and compliance with the Thai execution formalities. The best way to manage dual Wills is having separate Wills by district; have a UK Will for UK assets and a Thai Will for Thailand-based assets. Make sure that each Will clarifies that it applies only to its respective district to avoid contradictions (non-revocation clauses). Use solicitors in both countries to ensure local expertise and the RSM Law firm Thailand can assist you with all that you need to know about Thai Wills.

Taxes and inheritance

If you are domiciled in the UK, your worldwide assets are subject to UK IHT (inheritance tax); however, if you are not, only UK-based assets are subject to it. The inheritance tax is 40% and charges to estate over the threshold of £325,000 (nil-rate band). If you leave your assets to your spouse or civil partner, it is tax free. Additionally, if they die before you, their nil-rate band can be transferred to you, meaning your threshold could increase up to £650,000.

In Thailand, an inheritance tax only applies to the portion of inheritance exceeding THB 100 million per heir. Amounts above this threshold are taxed at 5% for lineal heirs (such as children or parents) and 10% for other heirs, while transfers to a lawful spouse are entirely tax-exempt. Thailand applies this tax on a worldwide basis only if the heir is a Thai national or a Thai tax resident. Where the heir is a foreigner and not resident in Thailand, only assets physically located in Thailand are subject to inheritance tax. It is also important to distinguish inheritance tax from income tax. While inheritance itself is not treated as taxable income under Thai law, any income derived from inherited assets located abroad (such as dividends, interest, or capital gains) will be subject to Thai personal income tax once the beneficiary qualifies as a Thai tax resident, and the funds are remitted into Thailand. This applies regardless of whether the remittance occurs in the same tax year or in a subsequent year.

Eligibility of Executors

In the UK, an executor can be any person over 18 (beneficiary, solicitor, etc), with a maximum of four. There is no legal requirement for them to be a resident of the UK; however, certain difficulties may arise if they are not. There is no need for court approval, executors must just apply for Grant of Probate.

In Thailand, an executor must be at least twenty years old, of sound mind, and not declared bankrupt or legally incapacitated. Under the CCC, being named as an executor in a Will does not in itself confer authority. The appointment must be formally approved by the Thai probate court before the executor has any legal power to act. Although foreigners may serve as executors, practical complications can arise. Unlike the UK, where court approval is not required, in Thailand the executor only acquires authority once appointed by order of the probate court.

Probate and administration process.

For both Thailand and UK there is court involvement in the probate process. In Thailand, the Grant of probate is issued by the Thai court after hearings and in the UK, the Probate Registry gives it. The UK probate is typically quicker and much simpler as the Thai process always involves court system. This means that a Thai lawyer is required to aid in navigating the court system, whereas in the UK, a solicitor is often used but is not always required.

Summary

Not having correctly documented and legally enforceable Wills for British expatriates residing in Thailand who have assets in both countries can lead to significant consequences. With RSM by your side you will be provided with a team of expert Thai lawyers who can guide you through the Will process.

RSM Thailand Key Contacts

Pardorn Suchiva
Managing Partner – RSM Thailand Law Firm

RSM (Thailand) Limited
E:[email protected]

Krit Komkrit
Associate Director

RSM (Thailand) Limited
E: [email protected]

Pataraporn Sirisopikun 
Senior Manager - Legal and China Practice

RSM (Thailand) Limited
E:  [email protected]